Method of treating photographic paper.



EDWARD ALBERT CUNNINGHAM,

OF AMBRIDGE, PENNSYLVANIA.

METHCD OF TREATING PHOTOGRAPHIG PAPER.

No. sugars.

Specification of Letters Patent.

Application filed December 11, 1908.

Patented s in 6, 1909. Serial N0. 167,008.

To all whom it may concern: it knmvn that I, EDWARD ALBERT CUN- NINGHAM,of Ainbridge, in the county of l Beaver and State of Pennsylvania, haveinvented a new and useful Method of Treating Photographic Paper, ofwhich the following is a specification. My invention relates tophotographic I paper, and has for its'object the treatment ofphotographic paper, to restore a printl which has been treated by theprocess described in U. S. Letters Patent No. 895,970, or aprocess'sirnilar thereto, to its original state.

My treatment is especially adapted for the treatment of paper used inwhat is known as the blue-printing process, since by its I application iam enabled to remove the deposit of metallic salts deposited on theoriginal l print, and restore it from a non-actinic to its originalactinic blue color. j In carrying out my invention, I treat the printwith a solution or solutions of one of the alkalies preferably ofammonia, which removes the metal deposited by the process covered byPatent No. 895,970 and changes the ferrous salts to an oxid. The printis then Washed and transferred to a solution or solutions of one of thecyanide, preferably potassiuui ferrocyanid acidified with one of i theacids preferably hydrochloric acid, which changes the ferric oxid toferric chlorid, this is 'then immediately precipitated by the cyanid asferrous ferrocyanid (Prussian blue). The print is then treated with asolution or solutions'of a salt of one of the I l l 'mctals which easilygives up'oxygen; prefcrab y potassium bichrornate. The print is thenWashed and dried in the usual manner.

I clain1:- y 1. The herein described method of treat I ing photographicprints, which coIisist in subjecting them to the'action of an alkaline lsolution to thereby change the ferrous salts therein to an oxid, thenfurther treating the prints to convert the oxid and cause theprecipitation of ferrous ferrocyanid, and then oxidizing; substantiallyas described.

2. The herein described method of treatl .ing photographic prints, whichconsists. in

first converting the ferrous salts therein to I forin oxid, thentreating with a cyanid solution containing hydrochloric acid to convertthe ferric oxid to ferric chlorid, andprecipihating the same as ferrousferrocyanid, and then oxidizing; substantially as described.

3. The herein described method of treating photographic prints, whichconsists in first converting the ferrous salts therein to ierric oxid,then treating with a cyanid solu" ing photographic prints, whichconsists treating the prints with an alkali solution to:

convert the ferrous salts of the prints into ferric oxid, thensubjecting the prints to an acidified cyanid solution, and finallytreating them with an oxidizing solution; substantially as described.

5. The herein described method of treating photographic prints, whichconsists in converting the ferrous salts therein into ferric oxid, bythe action of an alkali, then treating with a cyanid solution containinhydrocl'iloric acid to convert the ferric oXi into ferric chlorid, andprecipitating the same as ferrous ferro-cyanid, and then treating withan oxidizing solution; substantially as described.

6. The herein described method of treat? in'g photographic prints,whichconsis'ts in a solution of a salt of oneofthe metals which gives upoxygen; substantially as easily described.

lntestimony whereof, I have hereunto, set

my hand.

EDWARD ALBERT- CUNNINGHAM.

W'itnesses:

. LEE 0. JONES, E. M. KEELY, Sr.

i treating with an ammonia solution to con:

